Thermostat heater

ABSTRACT

A fluid heater unit comprising an elongate vertical immersible tubular body established of material having a high coefficient of expansion, an elongate drive member of material having a low coefficient of expansion extending longitudinally therethrough and fixed to the lower end thereof, an electric resistance heater unit in sealed engagement in and depending from the lower end of the body, a power supply above the body, power leads extending from the supply through the body and connected with the heater and a switch engaged in a lead and fixed above the body, said switch being operatively related to the upper end of the drive member whereby the switch is opened and closed in response to the vertical movement of the upper end of the drive member relative to the upper end of the body caused by thermal expansion and contraction of said body and member.

United States Patent Nickmeyer et al.

1 THERMOSTAT HEATER [75] Inventors: Walter V. Nickmeyer, Redlands;

Raymond L. Simmons, San Jacinto, both of Calif.

[73] Assignee: Rama Corporation, San Jacinto,

Calif.

[22] Filed: Mar. 10, 1975 [21] Appl. No: 556,648

[52] US. Cl. 219/523; 219/331; 219/512; 219/517; 337/394 [51] int. C1. H0513 3/06 [58] Field of Search 219/318, 328, 331, 337, 219/437, 512, 517,523, 544, 552; 337/383, 394-399; 338/240, 241

[56] References Cited UNITED STATES PATENTS 1,742,638 1/1930 Fichtner 219/512 X 2,039,641 5/1936 Fichtner 219/512 X 2,479,587 8/1949 Morris et a1. 219/512 2,506,768 5/1950 Bentz et a1 219/523 X 2,611,066 9/1952 Freeman 219/523 3,107,290 10/1963 Willinger.... 219/512 X 3,319,049 5/1967 Ulanet 219/523 Primary Examiner--Volodymyr Y. Mayewsky Attorney, Agent, or Firm-Georges A. Maxwell [57] ABSTRACT A fluid heater unit comprising an elongate vertical immersible tubular body established of material having a high coefficient of expansion, an elongate drive member of material having a low coefficient of expansion extending longitudinally therethrough and fixed to the lower end thereof, an electric resistance heater unit in sealed engagement in and depending from the lower end of the body, a power supply above the body. power leads extending from the supply through the body and connected with the heater and a switch engaged in a lead and fixed above the body, said switch being operatively related to the upper end of the drive member whereby the switch is opened and closed in response to the vertical movement of the upper end of the drive member relative to the upper end of the body caused by thermal expansion and contraction of said body and member,

22 3a :2/2 4 i J91, t

US. Patent Nov. 25, 1975 3 4 1 M 4 E E E 2 a! THERMOSTAT HEATER This invention has to do with an electric resistance heater unit for heating and maintaining fluids in a vessel at a predetermined temperature.

Throughout the arts, many different electric resistance heater means with various temperature control means related thereto have been provided to heat and maintain the temperature of liquids at some desired level.

The principal difficulty or problem associated with such means is to determine where the temperature readings for the control means can be taken most effectively. Such readings have been taken by separate thermometers or thermo probes projecting into the volumes of fluid being heated; by thermostatically controlled switches related to and sensing the temperatures of the walls of the vessels in which the fluids are deposited; and by thermo couplers related to the sheaths of cartridge type resistance heaters employed. A principal shortcoming found to exist in such temperature sensing means and their relationship with related structure resides in the fact that they are responsive to temperatures at a single point or extremely small area and often provide false readings, as regards the temperature of the entire volume of fluid. Other shortcomings in such means resides in the fact that to be effective, they require special vessels with which the heating and temperature sensing means or devices must be directly and permanently related and/or require the use of special and costly equipment.

There has long been a need and desire for an economical and practical unitary, removably probelike resistance heater unit engageable in substantially any, small, liquid receiving means to sense the temperature of the liquid being heated whereby the temperature of the liquid can be brought up to and maintained at a desired, predetermined temperature.

While a number of unitary removable, probetype liquid heater units are commercially available, no such units, with effective and dependable temperature responsive control means, are known by us to be commercially available or otherwise provided prior to the instant invention.

Such units, employing metal sheathed cartridge type heaters with thermo couples related to their sheaths have been provided and appear to be the most satisfactory form of temperature controlled heater units thus far provided. While such units are reasonably effective, they have been found to be wanting in that the thermo couples in such heaters are responsive to the temperatures of the heater sheaths, at one point thereof and tend to give false readings, with regard to the temperature of the volume of fluid in which the heaters are engaged or submerged. Accordingly, such units, while approaching a notable degree of effectiveness, are not wholly effective or dependable. Further, cartridge heaters, with integrated thermo couples, are extremely costly and require the provision of costly and/or complicated means, related to the thermo couples and power supply for the heaters, to put them into effective use.

An object and feature of our invention is to provide a novel electric resister heater unit with a cartridge heater and a temperature responsive control means which is such that it can be effectively engaged in a volume of fluid in substantially any upwardly opening ves- 2 se] and set to effectively heat and maintain the temperature of the fluid at a desired, predetermined tempera ture.

It is an object and a feature of our invention to provide a heater unit of the character referred to including novel temperature sensing means which is responsive to the temperature of the liquid with and in which the unit is related.

Another object and feature of our invention is to provide a unit of the character referred to wherein the temperature sensing means is a novel bi-metal structure having one metal part with substantial fluid contacting surface area in direct contact with the fluid to be heated, remote from the resistance heater, and which is related to the power supply for the heater whereby power to and resulting energizing of the heater is effected in response to the temperature of the fluid adjacent said remote extensive surface.

lt is yet another object and feature of our invention to provide a unit of the character referred to wherein the temperature sensing means is responsive to the temperature of fluid which is spaced a substantial distance from the heater whereby its capacity and effectiveness to sense or read the temperature of the fluid is substantially uneffected by the temperature of the heater.

A further object of the invention is to provide a unit of the character referred to wherein the temperature sensing means includes a novel, easy and economical to manufacture, service and maintain, switching and/or switch actuating means which are extremely dependable and desirable in operation.

The foregoing and other objects and features of our invention will be fully understood and will become apparent from the following detailed description ofa typi cal preferred form and application of our invention, throughout which description reference is made to the accompanying drawings, in which:

FIG. 1 is an isometric view of our heater unit, engaged in a vessel containing fluid to be heated;

FIG. 2 is a detailed sectional view taken as indicated by line 2-2 on FIG. 1;

FIG. 3 is a view taken as indicated by line 3--3 on FIG. 2;

FIG. 4 is a view taken as indicated by line 4-4 on FIG. 2;

FIG. 5 is a view taken as indicated by line 5-5 on FIG. 2;

FIG. 6 is a view taken as indicated by line 6-6 on FIG. 2; and

FIG. 7 is an enlarged isometric view of a portion of the structure shown on FIG. 2.

Referring to FIG. I of the drawings, the heater l-l that we provide is shown arranged in cooperative relationship with a vessel V containing a volume of liquid L and is shown connected with an electric service outlet 0.

The heater H, illustrated in detail in FIGS. 2 through 8 of the drawings includes generally, an elongate, vertical, tubular metal body 8 with upper and lower ends, an elongate, vertical cartridge resistance heater R, secured to the lower end of the body B and depending freely therefrom, a box-like housing or case C secured to the upper end of the body, an elongate, vertical, metal drive member M fixed to the lower end of the body and projecting into the case C, switch means S in the case operatively connected with the drive member M, and power supply means P extending into and through the case and the body and cooperatively connected with the switch means 5 and resistance heater At this time. it is important to note that the body B and the drive member M are made of different materials selected for their coefficients of expansion and that the member M has a notably greater or lesser coefficient of expansion than the body B. In the case illustrated, the coefficient of expansion of the member M is less than the coefficient of expansion of the body B.

In practice. while it is economically practical to establish both the body B and the member M of suitable metals, such as brass and stainless steel, one of said parts, for example, the member M could be established of a non-metallic material, such as porcelain.

The body B is a simple length of cylindrical tubular stock, open at its upper and lower ends.

The upper end of the body is provided with and carries a flat, horizontal, flange-like platform or deck 10, which deck is fixed to the body as by welding w and establishes a mounting means for the switch means S, and a bottom wall for the case C.

The lower end of the body B is shown swagged radially inwardly to engage the resistance heater R.

The resistance heater R is an elongate, vertical, cartridge type resistance heater with a cylindrical outer metal sheath 11 with a closed lower end 12 and an upper open end 13 from which a pair of elongate, spaced, substantially parallel contacts 14 and 15 project upwardly. The contacts 14 and 15 connect with a resistance element (not shown) which is arranged within the sheath and which is maintained in position therein by a body of compacted insulating material, within the sheath and about the element and contacts, in accordance with common practice.

The upper end portion of the resistance or cartridge heater R is engaged in the lower end portion of the body B in axial alignment therewith and with the lower, inwardly swagged end portion of the body in tight engagement about the sheath 11. The lower terminal end of the body is welded and sealed with the cartridge sheath 1] as by welding W.

In practice, it is possible that the body B might be made equal in inside diametric extent with the outside diametric extent of the cartridge heater, in which case the cartridge will slide in the body and the body need not be swagged inwardly, or might be less in diametric extent than the cartridge in which case the body might be welded directly to the upper end of the sheath or expanded to receive the sheath.

The case C is established by a downwardly opening box-like unit preferably molded by a suitable dialectric plastic material and in the case illustrated is characterized by flat, top, side and ends 20, 21 and 22. The side and end walls define a downwardly disposed lower edge 23 which opposes the top surface of the deck about the perimeter thereof and is releasably secured thereto by suitable screw fastener means 24.

In practice, a suitable gasket 25 is interposed between the deck 10 and case C to seal therewith and therebetween.

The case is further provided with a threaded adjusting screw opening 26 in its top wall 20 and a service cord or line access opening 27 in one of the end walls 22.

The drive member M is a simple, straight, elongate member arranged within and extending parallel with the body B, preferably adjacent one side thereof and has its lower end portion fixed thereto, as by welding w. The upper end portion of the member projects up- 4 wardly from within the body into the interior of the case C and is connected with the switch means S, as will hereafter be described.

The switch means S is shown as including, generally, a micro switch 30 mounted in the casein fixed position relative to the upper end of the body and an operating arm 31 with one end pivotally mounted, on an axis fixed relative to the upper end of the body and with its other end engageable with the micro switch. The arm 31 is drivingly coupled to the upper end of the drive member M whereby the arm is pivoted to swing and move its said other end relative to the switch 30 upon relative heat expansion and contraction of the body B and member M.

While it is possible and may be practical in some instances to operate the switch 30 by direct contact or engagement with the upper end of the member M, the amount of relative movement between the body B and member M resulting from heat expansion or contraction is frequently insufficient to effect operation of the switch. Accordingly, the means S that we provide is intended and functions to mechanically multiply the relative difference of expansion and contraction, or movement of the body B and member M, to that extent necessary to assure positive and dependable operation of the micro switch 30.

Specifically, the means S includes a vertical mounting bracket 32 fixed to the deck 10 at the top surface thereof and adjacent one side of the upper open end of the body and within one end of the case.

The means S next includes an elongate upper support arm 33 with a rear end fixed to the bracket. The arm 33 extends substantially horizontally from the bracket toward the other end of the case and has a forward free end with a downwardly turned, vertical mounting flange 33 to which the micro switch 30 is suitably fixed.

The support arm 33 is preferably established of resilient metal strap stock and has a downwardly turned mounting pad 36 at its rear end, fixed to the mounting bracket. The arm 33 extends freely forwardly in the case in spaced relationship above the upper open end of the body.

The micro switch 30 has a vertically shiftable operating stem 34 projecting freely downwardly below the arm 33 and, in accordance with common practice, can be provided with a setting screw 35 to adjust the vertical travel of the stem.

The means S next includes the aforementioned operating arm 31. The arm 31 is an elongate flat, bar-like member or part occurring in substantial parallel spaced relationship below the mounting arm 33. The arm 31 has a rear end pivotally supported at the mounting bracket 32 and a front end which projects below the switch 30 and establishes operating contact with the operating stem 34 of the switch.

The rear end of the arm is shown integrally joined with the lower end of the downwardly turned mounting pad 36 on the arm 33, which pad is fixed to the bracket 32. Pivotal mounting of the arm 31 is effected or afforded by suitably relieving or removing a suitable amount of the metal stock at the line of joinder or corner between the mounting pad and the arm, as illustrated, whereby the pad and arm are joined or connected by a narrow, flexible, integral tie 37 of the resilient strap stock establishing the arms 31, 33 and pad 36.

The rear portion of the arm 31 occurs above the upper end of the upper portion of the member M projecting into the case and is suitably drivingly connected with said member. In the case illustrated, the upper end portion of the member is suitably formed, as by machining, to project through an opening provided in the arm 31 and is rivet-headed, as shown, to connect the member and the arm together.

Finally, the means S includes an adjusting screw 38 to vary and/or adjust the vertical space between the switch 30 and the arm 31, that is, the forward end of the arm. The screw is an elongate vertical screw, with a suitably formed bearing tip 39 at its lower end to engage the top of the arm 33 and a manually engageable dial indicator knob 40 at its upper end. The screw is threaded in and through the opening 26 in the top of the case to project downwardly therein and engage the top of the forward end portion of the arm 33.

The arms 31 and 33 are normally forwardly divergent and the screw 38 serves to bias the forward end of the arm 33 downwardly to move the switch 30 into desired operating relationship with the arm 31.

It will be apparent that by vertical adjustment of the arm 33 and switch 31 in the above manner, the switch can be positioned so that it is actuated when the forward end of the arm 31 is moved vertically a predetermined distance. Since vertical movement of the arm 31 is directly responsive and proportional to the relative expansion and contraction of the body B and the member M, it will be apparent that by suitably adjusting the vertical position of the switch 30 by means of the screw 38, the operating temperature of the construction can be accurately and effectively adjusted, as desired, or as circumstances require.

The power supply P includes a dual line service cord 41 with a service outlet plug 42 engageable with a service outlet 0. The cord extends through the opening 27 in the case C. The opening 27 is provided with grommet 43 in accordance with common practice. The inner end portion of the cord within the case is, in accordance with common practice, divided to provide two elongate leads 44 and 45. The lead 44 extends through the case and thence downwardly through the body and is connected with the terminal 15 of the resistance cartridge heater R as by means of a butt connector. The lead 45 extends into the case C, is severed and connected with opposite terminals of the switches 30; that is, the switch 30 is engaged or interposed in the lead 44. The lead 44 extends from the switch 30 through the case C into the body 8 and can connect directly with the terminal 14 of the heater R in the same manner that the lead 44 connects with the terminal 15 or can, as shown, connect with the upper terminal end of an elongate vertical thermal fuse unit 50 arranged in the body, which fuse unit is supported in the body, in spaced relationship from the walls thereof by means of an elongate, extensible coil lead 51 between and connected with the terminal 14 and the lower terminal end of said fuse unit. The lead 44, unit 50, lead 51 and terminal 14 can be connected by means of butt connectors, as shown. The fuse unit 50 is responsive to heat generated by resistance in the power supply and opens when such heat becomes excessive, as when the heater terminals or resistance elements are shorted by liquid in which construction is engaged. The noted, or an equivalent, fuse means is required to meet safety requirements for such electrical devices or appliances.

In operation, when the fluid in which the structure is engaged is below desired temperature, the switch 30 is closed by the forward end of the operating arm 31, which is up and in operating pressure engagement with the stem 34 of the switch, thereby energizing the heater R. As the temperature of the fluid increases, the body B is heated thereby and expands in length or grows longitudinally relative member M as a result of its high coefficient of expansion. The drive member does not expand or grow appreciably in length markedly less than the body as the construction heats at its rate of growth. As a result of the above, the body B, the lower end of which is fixed to the lower end of the member M, draws the member M downwardly and pulls on the arm 31 downwardly at a point close to its pivotal axis, whereby the forward switch engaging forward end of the arm 31 is moved or swings downwardly and away from the switch a substantially greater distance. That is, a greater distance than the distance of relative longitudinal growth or expansion of the body A and member M. When the fluid and the body are heated to a predetermined desired temperature, the proportional extent of relative growth of the body B and member M is such that the operating arm 31 is moved downwardly to that extent necessary to open switch 30.

it will be apparent that as the fluid and body cool, the above rule of action is reversed and the switch is again closed. Accordingly, the construction is such that the switch is effectively opened and closed to maintain the liquid at a substantially uniform temperature.

It is to be particularly noted that the primary heat responsive member or part of the structure is the body B and that said body is heated by the fluid surrounding it, which fluid is remote from the heater R. Accordingly, the construction is not responsive to the temperature of the sheath of the heater or to the temperature of the fluid immediately adjacent thereto, but rather, is responsive to the temperature of the greater volume of the fluid remote from the heater R which surrounds the construction, that is, the body B thereof.

As a result of the above, the structure that we provide is far more effective to maintain a volume of fluid at a uniform temperature than other structures wherein the control temperature is read at or immediately adjacent to a resistance heater unit and is a far safer, easier and more convenient to use unit than can be approximated by apparatus comprising equivalent components in a separate loosely related manner.

it is to be noted that while some heat from the heater is directly absorbed by the lower end portion of the body and through the juncture between them, that heat is rapidly dissipated and absorbed by the surrounding fluid and does not extend far enough to adversely affect the desired operation of the invention.

A particular advantage afforded by this invention is the effective positioning of the whole of the heater element a substantial distance below the surface of the fluid whereby the cooler fluid which occurs in the lower portion of the vessel V as a result of convection currents is heated and the heated fluid, which rises as a result of such currents surrounds the temperature responsive body or elements of the construction.

Another advantage of our invention resides in the fact that the tubular, temperature responsive element or body B accommodates and encloses the parts and/or portions M l4, 15, 44, 45, 50 and 51 in a neat, compact, dry and safe manner, totally unaffected by the fluid.

Yet another advantage found in our invention resides in the fact that the body serves as a heat transfer means and is such that heat which might otherwise build up within the body and case to an undesirable or detrimental degree is dissipated through the body into the fluid surrounding the body. The amount of such internal heat normally encountered is not sufficient to adversely affect the operation of the construction so long as it is continuously dissipated in the above manner and is not allowed to accumulate.

Having described only one preferred form and carrying out of our invention. we do not wish to be limited to the specific details hereinabove set forth, but wish to reserve to ourselves any modifications and/or variations that may appear to those skilled in the art and which fall within the scope of the following claims:

Having described our invention, we claim:

1. An electric resistance fluid heater unit comprising an elongate vertical metallic tubular body with open upper and lower ends and established of material having a high coefficient of expansion. an elongate vertical drive member extending longitudinally through the body with a lower end and fixed to the lower end portion of the tubular body, a free upper end and established of material having a substantially lower coefficient of expansion than the body, a cartridge-type electric resistance heater unit in sealed engagement with and closing the lower end of the body and having a pair of terminals accessible within the body, a power supply cord extending from the unit at the exterior of the body and engageable with a power source, a pair of elongate leads extending from the cord into the body at the upper end thereof and each connected with a heater terminal and an adjustable switch engaged in one of said leads and arranged in fixed position relative to the upper end of the body, said switch being operatively related to the upper end of the drive member whereby the switch is opened and closed in response to the vertical movement of the upper end of the drive member relative to the upper end of the body caused by thermal expansion and contraction of said body and member, said body and heater being insertable in a volume of fluid to be heated, and a case of dielectric material fixed to and closing the upper end of the tubular body and enclosing the switch, said case having an opening through which said cord extends.

2. A structure as set forth in claim 1 wherein the switch has a vertically shiftable operating part and is spaced laterally from the upper end of the member and a structure which further includes an elongate operating arm with one end pivotally mounted in fixed position relative to the upper end of the body at a side of the member remote from the switch and extending transverse the axis of the member and drivingly engaged with the upper end of the member and with said operating part.

3. A structure as set forth in claim 2 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch.

4. A structure as set forth in claim 1 including manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.

5. A structure as set forth in claim 1 wherein the switch has a vertically shiftable operating part and is spaced laterally from the upper end of the member and a structure which further includes an elongate operating arm with one end pivotally mounted in fixed position relative to the upper end of the body at a side of the member remote from the switch and extending transverse the axis of the member and drivingly engaging the upper end of the member and said operating part, and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.

6. A structure as set forth in claim 2 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch; and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.

7. A structure as set forth in claim 1 and further including a thermal fuse engaged in one of said leads.

8. A structure as set forth in claim 1 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.

9. A structure as set forth in claim 8 and further including a thermal fuse engaged in one of said leads. 

1. An electric resistance fluid heater unit comprising an elongate vertical metallic tubular body with open upper and lower ends and established of material having a high coefficient of expansion, an elongate vertical drive member extending longitudinally through the body with a lower end and fixed to the lower end portion of the tubular body, a free upper end and established of material having a substantially lower coefficient of expansion than the body, a cartridge-type electric resistance heater unit in sealed engagement with and closing the lower end of the body and having a pair of terminals accessible within the body, a power supply cord extending from the unit at the exterior of the body and engageable with a power source, a pair of elongate leads extending from the cord into the body at the upper end thereof and each connected with a heater terminal and an adjustable switch engaged in one of said leads and arranged in fixed position relative to the upper end of the body, said switch being operatively related to the upper end of the drive member whereby the switch is opened and closed in response to the vertical movement of the upper end of the drive member relative to the upper end of the body caused by thermal expansion and contraction of said body and member, said body and heater being insertable in a volume of fluid to be heated, and a case of dielectric material fixed to and closing the upper end of the tubular body and enclosing the switch, said case having an opening through which said cord extends.
 2. A structure as set forth in claim 1 wherein the switch has a vertically shiftable operating part and is spaced laterally from the upper end of the member and a structure which further includes an elongate operating arm with one end pivotally mounted in fixed position relative to the upper end of the body at a side of the member remote from the switch and extending transverse the axis of the member and drivingly engaged with the upper end of the member and with said operating part.
 3. A structure as set forth in claim 2 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch.
 4. A structure as set forth in claim 1 including manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.
 5. A structure as set forth in claim 1 wherein the switch has a vertically shiftable operating part and is spaced laterally from the upper end of the member and a structure which further includes an elongate operating arm with one end pivotally mounted in fixed position relative to the upper end of the body at a side of the member remote from the switch and extending transverse the axis of the member and drivingly engaging the upper end of the member and said operating part, and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.
 6. A structure as set forth in claim 2 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch; and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.
 7. A structure as set forth in claim 1 and further including a thermal fuse engaged in one of said leads.
 8. A structure as set forth in claim 1 wherein the length of the arm between its point of engagement with the member and its said one end is less than its length between the point of engagement between the member and with the operative part whereby the movement of the members is mechanically increased by the arm at said switch and manually operable screw means carried by said case to selectively adjust the vertical position of the switch relative to the upper end of the body whereby the vertical movement between the upper ends of the body and member necessary to operate the switch can be varied.
 9. A structure as set forth in claim 8 and further including a thermal fuse engAged in one of said leads. 